Surface mounted integrated circuit packages are becoming increasingly popular in the semiconductor industry especially for VLSI circuits requiring a large number of terminals. Some popular surface mount technologies, include J-form, gull-wing, or area array configurations. The area array technologies normally comprise a packaged integrated circuit connected to a number of terminals protruding from the bottom of the integrated circuit package. These terminals can be pins, nearly spherical-shaped balls and/or column-type structures made from solder. These area array technologies, however, are expensive compared to other surface mount technologies.
Array surface mount technologies normally employ either ceramic materials or laminated printed circuit board materials. Metal lines and via holes transfer electrical contacts internal to the package and allow connection of each of the terminals to the integrated circuit die. Thus, packaging for area array surface mount technologies often includes multiple layers. Multiple layer packages are more difficult to design, more difficult to manufacture, and more costly than other surface mount technologies.
Other surface mount technologies for integrated circuit packages include dies attached to a lead frame enclosed by a plastic package and utilizing J-form or gull wing leads as terminals protruding from the perimeter of the package. Although less expensive and easier to manufacture than common area area array packages, integrated circuit packages using J-form and gull wing leads also suffer from several disadvantages. First, for a given surface area of the integrated circuit package, an area array integrated circuit package can have more terminals than J-form or gull wing integrated circuit packages.
Second, as manufacturers have increased the number of leads in integrated circuit packages employing J-form and gull wing-type leads, those leads have become closer together and have been constructed of thinner and narrower metal. Such construction leads to two problems. The leads are more easily damaged if the integrated circuit package is improperly handled or dropped. Also, the closeness of the leads increases the difficulty of soldering such an integrated circuit package to a circuit board.